This invention relates to compact optical imaging systems, and in particular to compact viewing heads in the insertion tubes of color video endoscope systems.
In color video endoscope systems the insertion tube of the endoscope includes a fiber optic light guide for directing light into the cavity to be viewed, an optical focusing section for gathering and focusing the reflected light, an image sensor for providing electrical output in response to the light input, electrical circuitry and connection means for triggering the image sensor and for transmitting signals back to a control unit, a biopsy channel, and water and air delivery channels. Because these features must all be present in the insertion tube of the endoscope and because the overall diameter of the insertion tube is limited by the human anatomy, it is important to optimize space utilization in the insertion tube.
In conventional color video endoscope systems the viewing head or imaging system at the distal end of the insertion tube usually comprises an optical focusing section and a solid state rectangular image sensor oriented perpendicular to the optical axis of the imaging system and to the central axis of the insertion tube. Associated circuitry to buffer the input to the image sensor and drive the output is separately supported and mounted in close proximity and behind the light-receiving face of the image sensor. Because the image sensor in such endoscopes is oriented perpendicular to the optical axis, the size of the image sensor is limited. In addition, since the image sensor provides a rectangular surface area greater than the circular surface area of the optical focusing section, it is difficult to package the biopsy channel, light guide and other features required to be contained within the insertion tube.